Same way you do when the sides are integers.
Example:
1 1/2 x 2 4/5 x 3 2/3
Step 1: First you turn the mixed numbers into improper fractions. (An easy way to do that is multiply the denominator by the whole number + the numerator.)
3/2 x 14/5 x 11/3
Step 2: Then you multiply the numerators.
3 x 14 x 11 = 462
Step 3: Then you multiply the denominators.
2 x 5 x 3 = 30
Step 4: Divide the numerator by the denominator
462/30 = 15 1/5
